[PATCH] D78151: [AArch64InstrInfo] Ignore debug insts in canInstrSubstituteCmpInstr

[Vedant Kumar via Phabricator via llvm-commits]

vsk created this revision.
vsk added reviewers: t.p.northover, eastig, paquette.
Herald added subscribers: danielkiss, hiraditya, kristof.beyls.
Herald added a project: LLVM.

Fix an issue where the presence of debug info could disable a peephole
optimization in optimizeCompareInstr due to canInstrSubstituteCmpInstr
returning the wrong result.

Depends on D78137 <https://reviews.llvm.org/D78137>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78151

Files:
  llvm/lib/CodeGen/PeepholeOptimizer.cpp
  llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
  llvm/test/CodeGen/AArch64/arm64-arm64-dead-def-elimination-flag.ll


Index: llvm/test/CodeGen/AArch64/arm64-arm64-dead-def-elimination-flag.ll
===================================================================
--- llvm/test/CodeGen/AArch64/arm64-arm64-dead-def-elimination-flag.ll
+++ llvm/test/CodeGen/AArch64/arm64-arm64-dead-def-elimination-flag.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=arm64-apple-ios7.0.0 -aarch64-enable-dead-defs=false < %s | FileCheck %s
+; RUN: llc -debugify-and-strip-all-safe -mtriple=arm64-apple-ios7.0.0 -aarch64-enable-dead-defs=false < %s | FileCheck %s
 
 target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
 
Index: llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -1447,6 +1447,8 @@
             E = CmpInstr->getParent()->instr_end();
        I != E; ++I) {
     const MachineInstr &Instr = *I;
+    if (Instr.isDebugInstr())
+      continue;
     if (Instr.readsRegister(AArch64::NZCV, TRI)) {
       AArch64CC::CondCode CC = findCondCodeUsedByInstr(Instr);
       if (CC == AArch64CC::Invalid) // Unsupported conditional instruction
Index: llvm/lib/CodeGen/PeepholeOptimizer.cpp
===================================================================
--- llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -614,6 +614,7 @@
     return false;
 
   // Attempt to optimize the comparison instruction.
+  LLVM_DEBUG(dbgs() << "Attempting to optimize compare: " << MI);
   if (TII->optimizeCompareInstr(MI, SrcReg, SrcReg2, CmpMask, CmpValue, MRI)) {
     ++NumCmps;
     return true;
@@ -635,6 +636,7 @@
     return false;
   if (!TII->optimizeSelect(MI, LocalMIs))
     return false;
+  LLVM_DEBUG(dbgs() << "Deleting select: " << MI);
   MI.eraseFromParent();
   ++NumSelects;
   return true;
@@ -1299,6 +1301,7 @@
   }
 
   // MI is now dead.
+  LLVM_DEBUG(dbgs() << "Deleting uncoalescable copy: " << MI);
   MI.eraseFromParent();
   ++NumUncoalescableCopies;
   return true;
@@ -1723,6 +1726,7 @@
           (foldRedundantCopy(*MI, CopySrcRegs, CopySrcMIs) ||
            foldRedundantNAPhysCopy(*MI, NAPhysToVirtMIs))) {
         LocalMIs.erase(MI);
+        LLVM_DEBUG(dbgs() << "Deleting redundant copy: " << *MI << "\n");
         MI->eraseFromParent();
         Changed = true;
         continue;


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